340 INVERTEBRATA OF MASSACHUSETTS. 



A'RGULUS ALO'S*:. An Argulus sent to me by Dr. T. W. 

 Harris, and procured by him from the gills of the alewife, (Jllosa 

 vulgdris,) I find to be new. As I have not since been able to 

 obtain specimens, I cannot give a detailed description ; but the 

 following characters will serve to distinguish it from other known 

 species. 



The shield is obovate or obcordate, covering only the first two 

 pairs of legs, which are so long that the fringed 

 fingers project entirely beyond it. Abdo- 

 men bearing the next three pairs of legs, 

 very narrow, and half as long as the shield. 

 Then follow two short folia, covered by two 

 others, each of them nearly as long and as 

 broad as the exposed part of the abdomen. 



It differs from A. foliaceus in having the 

 shield broader behind than before ; by its 

 extended abdomen, the shield in that species 

 covering all but the last pair of legs ; and by 

 the much greater length of the caudal appen- 

 dages. In A. Catastomi, the legs scarcely extend beyond the 

 margin of the shield, which is nearly circular, and rather broader 

 than long. Length about half an inch. 



CA'LIGUS PISCl'NUS, LATK. ; Hist. Nat. des Crust., iv. pi. 31, f. 1. 

 DESM. Monoculus piscinus, LIN.; FABR. 



This little fish-louse may be found, at almost any time, upon the 

 surface of the cod and other deep-water fishes, especially if the 

 fish is unhealthy. It has a small, rounded disc, about a fourth of 

 an inch in diameter, having two flattened, jointed appendages be- 

 hind, which are sometimes an inch in length, though they are 

 seldom found entire. 



I have another species of Caligus, quite different from the pre- 

 ceding, taken from a shark (Lamna punctata). It is remarkable 

 for having, within each posterior angle of the shield, two little 

 elevated crests, placed at right angles to each other. The abdom- 

 inal and caudal plates are very long and broad, and beyond these 

 the jointed appendages project, making the whole animal an inch 



